This invention relates to an idling control device for a high pressure fuel injection diesel engine and more particularly to an improved apparatus and method for controlling the idle condition in such engines.
As is well known, the typical diesel engine employs direct cylinder fuel injection. In conjunction with conventional diesel engines, the fuel injected at idle is injected for a relatively short duration, such as approximately 10.degree. of crank angle, and the ignition system must be set at a very early period for appropriate running of the engine. As a result, knocking increases. If, on the other hand, injection is delayed to avoid knocking, then poor combustion efficiency may result.
If the duration of fuel injection can be extended, then it is possible to overcome the aforenoted problems. This can be fuel injection nozzle. When an accumulator type fuel injection nozzle is employed, then the injection duration, even at idle, can be extended. For example, it is possible to start fuel injection at approximately 10.degree. before top dead center and terminate it as much as 30.degree. after top dead center. This can give rise to much improved combustion conditions and reduced knocking and improved combustion efficiency. However, it has been found that the manner in which the idle speed is controlled can be very critical on the engine performance.
It is, therefore, a principal object of this invention to provide an improved idling control device for high pressure fuel injection diesel engines and a method for operating such a device.
It is a further object of this invention to provide an idle injection control for a fuel injected diesel internal combustion engine wherein the idle speed can be controlled by selected strategies to improve the idle condition of the engine.